Microporous thermal insulation materials are materials which have a lattice structure in which the average interstitial dimension is less than the mean free path of the molecules of air or other gas in which the material is arranged. This results in a heat flow which is less than that attributable to the molecular heat diffusion of air or other gas in which the material is used. The lattice structure is created within a powder material by using a powder with very fine particles in a chain-like formation which adhere to each other. A suitable powder for providing this structure is finely divided silica in the forms normally referred to as silica aerogel or pyrogenic silica, although other materials are also available. The powder may be strengthened by the addition of a reinforcing fibre such as ceramic fibre and an opacifier may be added to provide infra-red opacification.
The microporous thermal insulation material may be formed into a panel by compressing the material. However, such a panel has limited strength and is friable and readily broken. The nature of the consolidated microporous thermal insulation material makes it particularly difficult to cause the material to bond to other substrates and this results in problems in the production of robust panels of microporous thermal insulation material.